The present invention generally relates to vehicle electrical systems and in particular to methods and circuitry for regulating vehicle control system voltages.
Mechanical linkage and hydraulic pressure operated controls for vehicles are well known in the art, and generally comprise control input devices operated by a user such as steering wheels, shift levers, and foot pedals which are directly interlinked with various vehicle controls individually or by combinations of mechanical push rods, gears, cables, or pressurized hydraulic systems. Such controls have been utilized in vehicles such as automobiles and trucks since the inception and initial manufacturer of such vehicles. As technology through the years has advanced, so also have these mechanical linkage and hydraulic pressure systems advanced with newer and more advanced innovations. Newer forms of technology wherein every vehicle now has one or more on-board computers in various forms assisting in vehicle operation and control. These computers through interconnection with various sensors and vehicle controls can rapidly acquire various objective input data, analyze this data, and then appropriately adjust the vehicle controls to more readily optimize the operation of the various vehicle systems and controls. As a result of the rapid computational power and speed of the computers, control commands can be issued at a much faster rate than older technology mechanical system configurations can respond. The requirement for increased control response time were initially felt in the aerospace industry where modern aircraft have evolved from the use of mechanically linked controls to electrically operated controls in a concept commonly known as xe2x80x9cfly-by-wirexe2x80x9d.
As the quest for more and more improvements in vehicle efficiency, more accurate controls, and improved response times, the automotive and vehicle industries are turning with greater frequency to additional electronics and electrical systems to provide necessary vehicle controls. Initially, implementation of various electrical control systems was limited to vehicle systems such as power windows and power door locks, the industry is now moving to replace mechanically operated, systems with electrically operated systems. Braking systems, for example, is potentially one such system. Previously, to ensure the integrity of a vehicle system such as brakes one only had to ensure that the mechanical linkages were secure and properly adjusted and that the brake hydraulic system also maintained its integrity. With the implementation of electrical and electronic controls, maintenance of electric power to vehicle systems is now paramount.
For example, by switching the vehicle braking system from one of mechanical linkages and hydraulic pressure systems to a purely electrical system, the only interconnection between the driver and the individual brakes at the four corners of the vehicle are electrical conductors. The input voltage to a load in such a system dips at the input terminals due to the current draw of the load through impedances from wiring, connectors, and the power source (battery or alternator). Large load current spikes cause severe voltage dips in the system, and some of these voltage dips may be severe enough to cause controller xe2x80x9cbrown outsxe2x80x9d or resets. Consequently, in a purely electrical control of a vehicle system special attention must be paid to the fail-safe conditions of the electrical system.
Therefore, maintaining operability during various system failure modes generally requires that some minimum amount of electric power be supplied to the various components to preclude the total loss of the system and potential loss of control of the vehicle as a result of the voltage xe2x80x9cbrown outsxe2x80x9d or controller resets. Such instances of power dissipation, voltage dips, and voltage transients which individually or in some combination can have the combined effect of failing to meet the basic functionality of the system. One such effect could be causing a microprocessor system to reset thereby causing that system or that portion of the system to go off-line and thus its function become unavailable to the vehicle operator. Similar problems exist in the event of the failure of the on-board electric power generation system such that the vehicle must rely strictly on available stored battery power. In this case, system availability remains paramount even though the systems must operate in a degraded mode to maintain that availability. Thus, there is a need to provide a methodology by which the basic characteristics of the electric power are maintained to prevent, to the greatest extent possible, the failure or operational cessation of electrical systems on a vehicle.
One aspect of the invention is a vehicle system incorporating a voltage regulating control. The system includes a power supply providing electrical power to the system and having a predefined maximum voltage. A controller controls an actuator performing a vehicle system function and the electrical load in the system wherein the controller has a first predefined minimum operating voltage. A voltage regulator communicates with the controller and the power supply and senses a control system input voltage in the control system. In response to a voltage dip in excess of a predetermined value, the regulator changes an effective electrical impedance of the control system to maintain the system voltage at a predefined minimum voltage greater than the first predefined minimum operating voltage required by the controller.
Another aspect of the invention is a method for regulating the voltage of a vehicle system of the type having a power supply, a controller, and an actuator. The method comprises the steps of defining a minimum system voltage; sensing a current demand for the system during operation of the actuator; increasing an effective impedance of the actuator when the sensed current demand approaches a predefined maximum; and limiting the system voltage to a predefined minimum.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.